196 
Outer surface with 40 radial, low, broad, round ribs, with 
linear interspaces, slightly crenulating the margin. Obsolete 
accremental growth-lines cross the ribs. The general colour 
is a sordid white, and the surface is mostly eroded. The 
interior is bordered with a narrow continuous band of a grey 
colour, articulated with 40 equidistant blackish-brown 
radially arranged spots, corresponding with the intercostal 
spaces. The spatula is well marked, bluish-white, with dis- 
tinct muscle-scars rather wide in front, so as to give it a 
decided neck, beyond which it projects with a convex end. 
The radula consists of 105 rows of teeth with the for- 
mula 2 (3.0.3.) 2, or more correctly 2 (14:1:0111) 2. The 
marginals are simple, bent nearly at a right angle in the 
middle, with straight stems and curved cusps. The outer 
laterals are in line with each other, the inner of the two is 
only about half as wide as the other, with distinct cusps but 
with united bases which (though the radula may be picked 
to pieces) are inseparable. The inner laterals are at a higher 
level, and are close to each other, but their bases are quite 
separable. ‘There is no central tooth. It has a triangular 
branchia extending from the left over the neck to the right, 
without any branchial cordon. 
Dimensions.—Length, 315 mm.; breadth, 23 mm.; 
height, 14 mm.; height of the curve at the border, 2°5 mm. 
Locality.—Type from Cape Naturaliste. 
It is found also in abundance on Rabbit Island, King 
George Sound, and at Ellensbrook and Yallingup, south of 
Cape Naturaliste. 
It lives on the shell of Patella neglecta, Gray. Nearly 
every example of which above 25 mm. in length carries one 
or more (hence its name). 
Variations.—It may grow to the size of 41 mm. long by 
32 mm. wide and 215 high. The ribs may increase to more 
than 50. 
The outer surface is generally much eroded, so that the 
apex is absent. In one example, 18 mm. by 13 mm. by 
5 mm., the top is a brown point without any sign of a spiral, 
‘5 mm. by ‘25 mm. in size surrounded by a white area 2 mm. 
by 1 mm., from which project 9 primary rays. These in- 
crease rapidly by splitting and by intercalation to 23 at the 
margin. 4 
The blackish markings inside the border vary with the 
number of ribs. They may be very distinct, but in the 
larger shells they fade out and may disappear altogether ; 
sometimes in the smaller shells they may be very faint. The | 
narrow marginal band may be so dark as to quite obscure 
